The present invention relates to an airflow indicator. More particularly, it relates to an airflow indicator for cooling a motor in a vacuum cleaner.
Typical vacuum cleaners load a suction motor more and more as the dirt bag/cup/container becomes full. Many vacuum systems use the air flow through the system in order to cool the motor (particularly in clean air type vacuums). As the dirt holding means of the vacuum becomes more and more full, there is less and less cooling air passing through the motor. The end result can be a reduced motor life due to increased loading. One attempt at remedying this problem is the use of a hold-open thermostat which shuts the unit off when the system airflow is not adequate to cool the motor.
The hold-open thermostat is used to prevent the motor from driving a brush roll of the vacuum cleaner once the motor has cooled down. A brush roll that engages when the cleaner is stationary is a safety hazard for an unsuspecting consumer evaluating the unit after it has shut off.
There are several reasons that the hold-open thermostat is not a good solution. Once the unit heats up to the trigger point, the consumer can no longer finish cleaning the carpet/surface. The fact that the unit will shut off and remain off for a period of thirty minutes or more is a big inconvenience to the consumer and therefore a product return issue as well.
Other vacuum systems have employed a bleed valve that opens an additional air path to the motor once the air flow through the motor is reduced to a certain level. The reduced (specified) level of airflow corresponds to a vacuum pressure value located at the bleed valve location. After some testing, a pressure value for the desired opening pressure is determined. Hence, a spring loaded valve is then designed to open once the pressure reaches the target value. Currently, vacuum system bleed valves employ a wire form spring. The wire form spring is part of an assembly which has a plunger that usually floats on the top end of the spring. The plunger also interfaces with another surface and commonly creates a seal based on the force of the compressed wire form spring.
Other vacuum manufacturers have used valves to indicate airflow to the consumer. Often this is done by displacement of a part once a certain pressure is achieved. Some vacuums have used a pin which displaces with the valve head once the open pressure is achieved. For instance, the pin displaces indicating that the final filter (often now a HEPA filter) may need replacement on the vacuum.
Although it is not exactly a valve, a full bag indicator has a plunger that moves in front of a clear window where it can be observed by the consumer. This change in position of the plunger is due to a pressure difference. The travel of the plunger is due to a small air hole which allows the plunger to move in the direction of the airflow. Since the airflow is so small, one can argue that the plunger operates on a static pressure difference.
Air valve springs often have low spring rates and large displacements once the desired opening pressure is reached. A larger spring rate usually translates to a system that is more sensitive to variations in assembly and manufacturing methods. Even though most air valves are designed with low spring rates, there are many inherent difficulties in achieving a system that performs accurately and precisely. The wire form spring design approach has many challenges. Often times, variations in plastic part dimensions prevent consistent compression. Variations in the wire form manufacture are costly to minimize and often require the use of precision springs. Even then, the variations expected with regard to the performance of an air valve are large. Often times, the displacement of the valve is different from valve to valve, and this can result in different airflow rates into the bleed valve. In fact, many air valve manufacturers actually inspect 100% of all of the assemblies that they ship.
Finally, once the air valve opens, it is often difficult to have the valve close at a desired pressure that is different than the opening value and ideal for customer use. The bleed valve will open under the sealed suction condition, and this often occurs intermittently when the consumer is cleaning furniture or using hand tools with the vacuum. Hence, it is desirable to have the valve close back up unless the filter needs cleaning. Again, it is very difficult to try to control the close value of a valve system that uses a wire form spring. Sometimes the valve will remain open due to the airflow through the valve. Finally, it is clear that friction is always a factor in a system that relies on surface-to-surface travel or displacement.
Accordingly, it has been considered desirable to develop a new and improved airflow indicator which would overcome the foregoing difficulties and others while producing better and more advantageous overall results.
The present invention relates to an airflow indicator. More particularly, it relates to an improved airflow indicator which provides additional air flow to cool off a motor of a suction device, such as a vacuum cleaner.
In the first preferred embodiment, an airflow indicator for a vacuum cleaner comprises a housing with a first end and a second end. The housing is comprised of a first section and a second section. The housing is fabricated from a plastic material. The housing can further comprises a pair of mounting holes for mounting the valve within the vacuum cleaner.
A wheel chamber is defined in the housing. A rotatable wheel is mounted in the wheel chamber at the housing first end. The wheel has protrusions which cause the wheel to rotate due to inlet air flow.
The wheel further comprises markings which gradually increase in size along an outside perimeter of the wheel. The markings indicate movement of the wheel.
An air inlet is formed at the first end of the housing. An air passageway is formed within the housing adjacent the rotatable wheel and the air inlet. An air outlet is formed at the second end of the housing.
A valve is mounted within the housing adjacent the air passageway. The valve comprises a cross slit which opens in response to a change in vacuum pressure. The cross slit remains closed at a pressure difference less than 56 inches of H2O.
If preferred, the valve is fabricated from a silicon composite.
If desired, the airflow indicator further comprises a window portion which partially encloses the wheel within the wheel chamber. The window allows viewing of the wheel from outside of the housing.
The air passageway comprises a curved passageway within the housing to facilitate air flow along the protrusions of the wheel.
One advantage of the present invention is the provision of a new and improved airflow indicator for a home appliance, such as a vacuum cleaner.
Another advantage of the present invention is the provision of an airflow indicator having a rotatable wheel with protrusions mounted in a wheel chamber of a housing of the airflow indicator where airflow contacts the protrusions of the wheel causing the wheel to rotate.
Yet another advantage of the present invention is the provision of an airflow indicator having a window in the wheel chamber and a wheel with markings where the markings increase from smaller to larger sizes and are visible through the window to indicate movement of the wheel to the consumer.
Still another advantage of the present invention is the provision of an airflow indicator having a curved air passageway found within the housing to facilitate airflow along the protrusions of the wheel.
Still yet another advantage of the present invention is the provision of an airflow indicator having a valve mounted within the housing. The valve is made from a resilient material and includes cross slits which open in response to a change in vacuum pressure.
Still other advantages and benefits of the invention will become apparent to those skilled in the art upon a reading and understanding of the following detailed description.